This invention relates to a method and apparatus for sealing reopenable cable splice closures in both pressurised and non-pressurised networks.
Reopenable splice closures are used for jointing cables and for the distribution of branch cables. The closure effects environmental protection and sealing of the cable joints, which cables may be telecommunications and optical fibre cables and the joints may be between adjacent lengths of cable or at their connection to terminal accessories.
Various techniques are known for sealing reopenable splice closures. These include the use of heatshrink polymer members, self-amalgamating tapes, mechanical rubber seals and self-curing resins. One or more of these techniques are used to seal or re-seal a closure after re-entry for the maintenance of internal splices or to fit an additional cable for splicing to existing cables. The environmental sealing is carried out in two distinct areas, firstly the closure or sleeve for re-entry to the internal elements of the closure, secondly the cable entry ports.
The above techniques have various disadvantages. For example, although heatshrink members provide a seal of high performance for both unpressurised and pressurised cables over a relatively large cable range, re-entry to the closure body requires the addition of new materials at extra expense and inconvenience, and the existing cable entry ports require adequate protection from heat when recovering the heatshrink members for sealing additional cables to the entry ports. Self-amalgamating tapes require considerable care and dexterity on the part of the operator, both to ensure that adequate tape has been provided and to cover all surfaces so that even the smallest gap or moisture penetration path is avoided. Other notable disadvantages of self amalgamating tapes are (a) the inflexibility in the range of cable diameters that can be used for a single port size, (b) the ability of the tape material to move or creep with normal environmental vibration or internal air pressure particularly at elevated temperatures, and (c) the need to replace sealing tape at extra expense and inconvenience when re-entry is required to either the closure body or cable entry ports.
Mechanical rubber seals can effect a seal of high performance for both unpressurised and pressurised cables without the need for additional materials for reclosing after entry. Mechanical rubber seal clamp assemblies are typically designed with one fixing thumb screw facilitating ease and speed of re-entry. However, this technique has the disadvantages that the rubber seal is only effective if clean (a potential hazard in external use) and the seal mating faces have to be dimensionally stable (a constraint when using cables of various sizes and shapes e.g. oval).
Self curing resins provide a poor means of environmental seal over long periods of time, particularly over the life of a cable jointing closure of 20-30 years. Resins have the disadvantage that they require adequate time to cure and that the contact with skin and the fumes which are given off are potential health hazards. The notable advantage with resins over other sealing techniques is that they flow around the cables at the entry port, producing an effective barrier to gas, moisture and water and to cable grease penetration.